Muscle Cramps : When we use the muscles that can voluntarily be controlled, such as those of our arms and legs, they alternately contract and relax as we move our limbs. Muscles that support our head, neck, and trunk contract similarly in a synchronized fashion to maintain our posture. A muscle (or even a few fibers of a muscle) that involuntarily (without consciously willing it) contracts is called a "spasm." If the spasm is forceful and sustained, it becomes a cramp. A muscle cramp is thus defined as an involuntarily and forcibly contracted muscle that does not relax. Muscle cramps can last anywhere from a few seconds to a quarter of an hour, and occasionally longer. It is not uncommon for a cramp to recur multiple times until it finally goes away. The cramp may involve a part of a muscle, the entire muscle, or several muscles that usually act together, such as those that flex adjacent fingers. Some cramps involve the simultaneous contraction of muscles that ordinarily move body parts in opposite directions. Cramps are extremely common. Almost everyone experiences a cramp at some time in their life. Cramps are common in adults and become increasingly frequent with aging. However, children also experience cramps. Any of the muscles that are under our voluntary control (skeletal muscles) can cramp. Cramps of the extremities, especially the legs and feet, and most particularly the calf (the classic "charley horse"), are very common. Involuntary muscles of the various organs (uterus, blood vessel wall, intestinal tract, bile and urine passages, bronchial tree, etc.) are also subject to cramps. Cramps of the involuntary muscles will not be further considered in this review. This article focuses on cramps of skeletal muscle.

Common Causes of Cramps : Numerous medicines can cause cramps. Potent diuretic medications, such as furosemide (Lasix), or the vigorous removal of body fluids even with less potent diuretics can induce cramps by depleting body fluid and sodium. Simultaneously, diuretics often cause the loss of potassium, calcium, and magnesium, which can also cause cramps. Several vitamin deficiency states may directly or indirectly lead to muscle cramps. These include deficiencies of thiamine (B1), pantothenic acid (B5), and pyridoxine (B6). Poor circulation to the legs, which results in inadequate oxygen to the muscle tissue, can cause severe pain in the muscle. This commonly occurs in the calf muscles. While the pain feels virtually identical to that of a severely cramped muscle, the pain does not seem to be a result of the actual muscle cramping. This pain may be due to accumulation of lactic acid and other chemicals in the muscle tissues.

Treatment of skeletal muscle cramps : Most cramps can be stopped if the muscle can be stretched. For many cramps of the feet and legs, this stretching can often be accomplished by standing up and walking around. For a calf muscle cramp, the person can stand about 2 to 2½ feet from a wall (possibly farther for a tall person) and lean into the wall to place the forearms against the wall with the knees and back straight and the heels in contact with the floor. (Learn this maneuver at a time when you don't have the cramp!) Another technique involves pulling the toes up towards the head while still lying in bed with the leg as straight as possible. For cramps such as those that occur in writer's cramp, pressing the hand on a flat surface will stretch the cramping finger flexor muscles. Gently massaging the muscle will often help it to relax, as will applying warmth from a heating pad or hot soak. Interestingly, since the normal response of the muscle to cold is to shorten, ice packs may also relax a cramp. If the cramp is associated with fluid loss -- as is often the case with vigorous physical activity -- fluid and electrolyte (especially sodium and potassium) replacement is essential. Medicines are not generally needed to treat an ordinary cramp that is already present, since most cramps subside spontaneously before enough medicine would be absorbed to even have an effect. One enthusiastic non-scientific recommendation has been to firmly pinch the tissues above the lip, just under the nose, and hold the pinch until the cramp stops (said to be within 15 minutes.) Of course, why this might work, or even if it is causing anything that wouldn't have happened anyway, is uncertain, and no scientific study of this technique has been reported. In recent years, injections of therapeutic doses of botulism toxin have been used successfully for some dystonic muscle disorders that are localized to a limited group of muscles. A good response may last several months or more, and the injection may then be repeated. The treatment of cramps that are associated with specific medical conditions generally focuses on treating the underlying condition. Sometimes, additional medications specifically for cramps are prescribed with certain of these conditions. Of course, if cramps are severe, frequent, persistent, respond poorly to simple treatments, or are not associated with an obvious cause, the patient and the doctor need to consider the possibility that more intensive treatment is indicated or that the cramps are a manifestation of another disease. As alluded to above, the possibilities are extremely varied and include problems with circulation, nerves, metabolism, hormones, medications, and nutrition. It is not common that muscle cramps would result from a medical condition without some other obvious signs that the medical condition is present. In the long run, however, the most important aspect of dealing with common muscle cramp disorders is prevention.

Types of Cramps : There are four major types of skeletal muscle cramps according to McGee (1). These include "true" cramps, tetany, contractures, and dystonic cramps. Cramps are categorized according to their different causes and the muscle groups they affect. "True" Cramps : "True" cramps involve part or all of a single muscle or a group of muscles that generally act together, such as the muscles that flex several adjacent fingers. Most authorities agree that "true" cramps are caused by hyperexcitability of the nerves that stimulate the muscles. They are overwhelmingly the most common type of skeletal muscle cramps. Tetany : In tetany, all of the nerve cells in the body are activated, which then stimulate the muscles. This reaction causes spasms or cramps throughout the body. The name tetany is derived from the effect of the tetanus toxin on the nerves. However, the name is now commonly applied to muscle cramping from other conditions, such as low blood levels of calcium and magnesium. Low calcium and low magnesium, which increase the activity of nerve tissue non-specifically, also can produce tetanic cramps. Often, such cramps are accompanied by evidence of hyperactivity of other nerve functions in addition to muscle stimulation. For instance, low blood calcium causes not only spasm of the muscles of the hands and wrists, but also a sensation of numbness and tingling around the mouth and other areas. Contractures : Contractures result when the muscles are unable to relax. The constant spasms are caused by a depletion of adenosine triphosphate (ATP), an energy chemical within the cell. This prevents muscle fiber relaxation. The nerves are inactive in this form of muscle spasm. Contractures can be inherited (e.g., McArdle's disease -- a defect of the breakdown of glycogen to sugar within the muscle cell) or acquired (e.g. hyperthyroid myopathy -- a muscle disease that is associated with an overactive thyroid). Cramps of this category are uncommon. Dystonic Cramps The final category is dystonic cramps, in which muscles that are not needed for the intended movement are stimulated to contract. Muscles that are affected by this type of cramping include those that ordinarily work in the opposite direction of the intended movement, and/or others that exaggerate the movement. Some dystonic cramps usually affect small groups of muscles (eyelids, jaws, neck, larynx, etc.) The hands and arms may be affected during the performance of repetitive activities such as those associated with handwriting (writer's cramp), typing, playing certain musical instruments, and many others. Each of these repetitive activities may also produce "true" cramps from muscle fatigue. Dystonic cramps are not as common as "true" cramps.